[49.03] Ice chemistry on the Saturnian satellites

M.L. Delitsky, A.L. Lane (JPL)

The magnetosphere of Saturn contains plasma ions that have
flows inwards and outwards of the planet, as measured by
Voyager. These ions impact the satellites and induce
chemistry in their surfaces. Voyager measured such species
as O+, H2O+ (and other water group ions), N+,
N2+, H+ and others, as well as electrons. If N+
and N2+ ions from Titan sputtering reach the inner
satellites Rhea, Dione, Tethys, Enceladus and Mimas,
implanting of these ions into the water ice surfaces should
induce a complex nitrogen oxides chemistry. Species observed
in laboratory experiments of N+ impact into water ice
include NO, NO2, NO3, HNO2, HNO3, NH2OH, HNO,
NH, and NH2. Impact of N2+ will yield N2O, HNNO,
and N2. If the surfaces also include CO2 (which is a
possible volatile already observed on the Jovian
satellites), then other species that may be formed as a
result of N+ impact into H2O/CO2 ice will be HNCO,
NCO and R-OCN. The simplest molecule, NO (nitric oxide),
should have an appreciable vapor pressure at Saturnian
satellite temperatures. At 90 K (a typical temp for
Saturnian satellites), the vapor pressure of NO is about 4
millibar. At 105 K, its v.p. would be 98 millibar. This
should be observable with high-resolution instruments.